Microcontroller units (or MCUs) can be used in wide variety of applications to control the operation of complex systems. For example, an MCU can be used in an automotive environment to control the operation of vehicle subsystems, such as an inflatable restraint system or a climate control system. When used in such environments, the MCU can be required to monitor the operation of system components by measuring (or sampling) signals used or produced by the components. Often these signals can be analog signals, which are generally defined as signals that are time-varying and continuous.
The analog signals can be sampled and the samples converted to digital values (logical xe2x80x9conesxe2x80x9d and xe2x80x9czeroesxe2x80x9d) using an analog-to-digital (A/D) converter. The A/D converter can be included on an integrated circuit (IC) chip along with the MCU, and the digital values produced by the A/D converter can be used by the MCU to monitor and control the operation of the components. The number of analog signals that can be required to be converted into digital values to monitor and control the operation of a complex system can be great. An MCU IC chip can include a large number of input pins (or terminals) to receive the analog signals.
A single xe2x80x9con-chipxe2x80x9d A/D converter can be used to sample the analog signals presented at several of the input terminals. A control signal, often referred to as a xe2x80x9ctriggerxe2x80x9d, can be used to initiate a conversion. The A/D converter can be configured to operate in a particular manner (or mode) prior to the occurrence of a triggering event. For example, the A/D converter can be configured prior to the occurrence of multiple triggering events to sequentially convert the analog signals presented at several of the input terminals (referred to here as a xe2x80x9csweepxe2x80x9d mode). The A/D converter can also be configured to convert the analog signal presented at only one of the input terminals (referred to here as a xe2x80x9cone-shotxe2x80x9d mode), such that the later occurrence of multiple triggering events can result in the repeated conversion of the analog signal presented at the one input terminal.
Some applications can require a capability to convert the analog signals presented at two or more inputs with relative precise timing. To accomplish this, A/D converters operating in the sweep mode can be configured to pause after converting the analog signal presented at one of the input terminals included in the sweep, and to wait for a second occurrence of the trigger to occur to resume and complete the sweep. U.S. Pat. No. 5,302,952 to Campbell, Jr., et al. describes an A/D conversion module and method to minimize software involvement by providing a pause capacity. U.S. Pat. No. 5,291,197 to Abe describes a one-chip data processor with built-in A/D converter for automatically repeating A/D conversions without instructions from a central processing unit (CPU).
Techniques are disclosed for analog-to-digital signal conversion. According to an exemplary embodiment, a first request is associated with a plurality of input terminals and a second request is associated with one of the input terminals. An analog signal presented at each of a portion of the input terminals associated with the first request is converted in succession into a digital value until the one of the input terminals associated with the second request is reached. A predetermined amount of time is waited to receive the second request. An analog signal presented at each of a remaining portion of the input terminals associated with the first request is converted in succession into a digital value when one of an expiration of the predetermined amount of time and a receiving of the second request occurs.